Recently, in order to eliminate break of transmission of the mechanical power when shifting gears, a so-called dual clutch transmission provided with a first clutch capable of engaging an input shaft of a first transmission mechanism composed of odd-number gear positions (hereinafter, referred to as a first input shaft) with an output shaft of the internal-combustion engine (hereinafter, referred to as an engine output shaft), and a second clutch capable of engaging an input shaft of a second transmission mechanism composed of even-number gear positions (hereinafter, referred to as a second input shaft) with the engine output shaft, and shift gears by alternately engaging the two clutches is known as a transmission for the vehicle (for example, refer to Patent Documents 1 to 3).
The dual clutch transmission prevents the break of the power transmission when shifting gears by allowing an even-number gear pair to mesh with each other in advance and putting the first clutch, which transmits the mechanical power to the odd-number position, into a release state, and putting the second clutch, which transmits the mechanical power to the even-number position, into an engaging state, when shifting from the odd-number position to the even-number position, for example.
Also, the following Patent Document 1 discloses the dual clutch transmission (double clutch gear device) provided with the two transmission mechanisms as described above and with an electric motor (second drive unit) engaging with the input shaft (second input shaft) of one transmission mechanism (second gear unit). The Patent Document 1 discloses to perform cranking to start the internal-combustion engine by putting the second clutch into the engaging state and transmitting the mechanical power output from the second drive unit to the second input shaft from the second clutch to the engine. Also, the Patent Document 1 discloses to allow the vehicle to travel by putting the first and second clutches into a non-engaging state (non-fastening state) and output the mechanical power from the second drive unit through the second transmission mechanism (second gear unit).
Also, the following Patent Documents 2 and 3 disclose the vehicle in which first and second motors are connected to the first and second input shafts of the dual clutch transmission, respectively. It is proposed to minimize maximum torque required for the motor by providing the motor on each input shaft.                Patent Document 1: Japanese Patent Application Laid-open No. 2006-312445        Patent Document 2: Japanese Patent Application Laid-open No. 2003-79005        Patent Document 3: U.S. Patent Application Publication No. 2002/0189397 Specification        